Since the 1980s, semiconductor laser and digital circuit have made significant progress, based on which the laser ranging technology has become more and more widely used in the fields of electricity, water conservation, telecommunications, environment, construction, police, firefighting, blasting, marine, railways, military terrorism, etc.
In the time interval measurement of pulsed laser ranging, a direct counting method of a digital clock is generally adopted to calculate the time interval between laser emission pulse and received pulse, thereby obtaining the distance of a measured target. As the measured time interval is random, the number of clock cycles calculated by such a counter has errors and hence influences ranging accuracy.
However, as phase measurement requires one inner optical path reference signal, the internal structure and control method of a ranging device becomes complicated, increasing the manufacturing cost of the ranging device while not being conductive to miniaturization development of the ranging device.